In the course of activating or driving of a motor, when a motor is constrained (or in similar abnormal states) due to a certain factor (the motor suppressed by a hand, for example), a motor driving device or the motor may be damaged by the current continuously flowing into specific phases (e.g. from phase U to phase V).
A constraint protection circuit is embedded in a conventional motor driving device. When there is no indication of a FG (frequency generator) signal (a motor rotation speed signal) generated within a predetermined time period, the constraint protection circuit will identify the motor being in the constraint state and force stop the driving of the motor.
In addition, the patent literature 1 is an example relating to the present disclosure.